Wonder that you have the plastic freewheel...it's hard to notice wear on these...Can you tell if the teeth of the belt are looking like so?I mean - it looks like the teeth are not symmetrical - or is it just an optical illusion?

No rain during 4 days in France : no problem.But today, rain was back.. and the belt went off.

I analysed and I think I understand the problem.The snubber seems not to be centered, and when it is rainy, some dirty elements from the road are sticking on the belt. Then the belt and these elements touch the snubber more firmly, and the belt goes to the space on the left.

Hi, is the snubber bearing centered on the freewheel?It looks to me the belt is not centered on the freewheel. A quick check of the Stridas I have in stock most of them the belt is not centered with the belt running closer to the inside edge of the freewheel. It looks to me from your photos your belt is running closer to the outer edge of the freewheel.

Assumed that there is in fact no seal I'd think that all those little steel balls - which are most likely very close to the gap - are still more or less intact, but their diameter is smaller than it should be.